Such controllable two-way valve devices are known in particular as combined exhaust gas recirculation- and bypass valve devices in which two valve members are actuated via an actuator in order to reduce the pollutant emissions of a combustion engine, in that in the warm-up period the exhaust gas is conducted via the bypass and after a catalyst has heated up, the exhaust gas is recirculated via the EGR cooler.
Thus in DE 100 25 877 an exhaust gas recirculation system is described with a valve device that features one exhaust gas inlet and two exhaust gas outlets, whereby one of the exhaust gas outlets leads to a cooler and the other exhaust gas outlet leads to a bypass channel bypassing the cooler. On a housing of the valve, a valve seat is arranged respectively between the exhaust gas inlet and the two exhaust gas outlets, which valve seat is governed by a disk-shaped valve member. A valve member is arranged thereby on an inner valve rod that can be moved via the actuator, and the second valve member arranged nearer to the actuator is arranged in a permanent manner on a second tubular valve rod bypassing the first valve rod. The actuator is embodied thereby such that two springs are arranged in the actuator via which the two valve disks are pressed onto their valve seats tensioned. The inner and the outer valve rod are each arranged so that they can be displaced with respect to one another, so that the pneumatic or electromotive actuator is embodied such that, depending on the direction of movement, only one of the valve rods and thus also only one of the valve members is lifted from the valve seat.
In DE 198 12 702 A1 a valve arrangement for the control of a recirculated exhaust gas stream is likewise described, whereby this is arranged behind a bypass channel or an exhaust gas cooler respectively, so this features two inlets and one outlet. The two valve members corresponding respectively to a valve seat are respectively pressed onto the valve seat via two coil springs arranged in the channel. Both valve members feature a hole in the center through which a common valve rod extends at least partially. The valve rod features two collars via which, when the valve rod is actuated, the valve members can be actuated respectively individually via the collar in the direction of opening against the spring force, whereby the respective other valve member is to slide on the valve rod, since it is pressed farther onto the valve seat by means of spring force.
DE 197 33 964 A1 describes a similar valve arrangement, whereby the tensioning of the two valve disks is achieved here via a spring arranged between the two valve disks, so that the two collars of the valve rod are respectively arranged at the end of the valve disks opposite the spring.
The disadvantage of the above-mentioned embodiments is that either two valve rods, and thus correspondingly complex actuators are required, for displacement of the valve rods independent of one another, or in the embodiment with a single valve rod, the valve members are not arranged in a permanent manner on the rod, and thus do not occupy a defined position in the housing. Moreover such a valve arrangement is very sensitive to dirt, because the coil springs are arranged in the area through which exhaust gas flows, and also in the area through which exhaust gas flows the valve rod extends through the valve holes and must be moved there. Deposits can form on the valve rod due to carbon, so that a flawless function, namely a sliding of the valve rod in the holes of the valve members is no longer ensured. Moreover, in all embodiments only one of the two inlets or outlets can be opened, so that it is not possible for the exhaust gas to flow through the cooler and the bypass channel simultaneously, as a result of which mixed temperatures cannot be achieved. Due to exhaust gas pulsations occurring at the valve, the spring force for a reliable closure of the channels must be selected to be very high so that the actuator must also exert high forces during opening against the spring force, and thus must be embodied large and cost-intensive.
It is therefore an object of the invention to create a controllable two-way valve device controlled by a simple actuator, which device features only one valve rod and in which it is possible to control both outlet streams or inlet streams individually and independently of one another, and to interrupt an exhaust gas recirculation completely and reliably in spite of occurring gas pulsations. Moreover, the valve is to be as insensitive as possible to dirt and is to be cost-effective to produce and to assemble. In a preferred embodiment, it is also to be possible for partial streams to be conducted through the exhaust gas cooler or the bypass channel, respectively, so that mixed temperatures can be run.